The scientists - from the Vaudois University Hospital Centre (CHUV) in Lausanne, Switzerland - carried out a detailed examination of Arafat's medical records, samples taken from his remains and items he had taken into the hospital in Paris where he died in 2004.

The biological materials included pieces of Mr Arafat's bones and soil samples from around his corpse.

The scientists concluded that their results "moderately support the proposition that the death was the consequence of poisoning with polonium-210".

The scientists stressed that they had been unable to reach a more definitive conclusion because of the time that had lapsed since Arafat's death, the limited samples available and the confused "chain of custody" of some of the specimens.

Polonium-210 is a highly radioactive substance. It is found naturally in low doses in food and in the body, but can be fatal if ingested in high doses.

The scientists have made "a pretty strong statement", according to Prof Paddy Regan, an expert in radiation detection and measurement at the University of Surrey in the UK, who was not involved in the investigation.

"They are saying the hypothesis that Arafat was poisoned with polonium-210 is valid and has not been disproven by the data. However they cannot say definitively that he was murdered."

Prof Regan says a series of assumptions would have been made in order to ascertain how much Po-210 may or may not have been in Mr Arafat's body at the time of his death.

Po-210 has a short half-life of about 138 days.

Prof Regan said measuring the tiny fraction left and extrapolating it back to the time of Arafat's death was like a blind man holding the tail of an elephant and using the information to work out the size of the animal.

The second problem, he said, was that Po-210 occurs naturally in the environment. However, an indicator that the polonium may be synthetic is if there was far less Pb-210 (lead-210) in the samples.

The professor highlighted results from two samples - the shroud under the corpse of Mr Arafat and urine samples taken from his underwear - both showed high levels of Po-210 compared to Pb-210, possibly suggesting the presence of "additional" synthetic polonium.

He noted however that most of the samples of polonium measured in the report were accompanied by activities from Pb-210.

Parallel investigations are being carried out by French and Russian experts - one Russian official said last month that no traces of polonium had been found.

Yigal Palmor of Israel's foreign ministry told the BBC: "This is more soap opera than science."

Arafat's tomb in Ramallah was opened in private in November last year

He said the investigations had been commissioned by "interested parties" - Mr Arafat's widow and the Palestinian Authority - and had "never bothered" to look for some key data.

"The other huge hole in the theory is the absence of all access to the French hospital where Arafat died and to Arafat's medical files," said Mr Palmor.

"How can the cause of death be determined without the opinion of the doctors or the results of the medical tests they ran on the patient?

His widow had objected to a post-mortem at the time of his death, but asked the Palestinian Authority to permit the exhumation "to reveal the truth".

His remains were removed from his tomb in the West Bank city of Ramallah in November 2012 and reinterred the same day.

Last month, the head of the Russian Federal Medico-Biological Agency, Vladimir Uiba, was quoted by the Interfax news agency as saying that Arafat "could not have been poisoned with polonium", saying that test carried out by Russian experts "found no traces of this substance".

However, the agency later denied that Mr Uiba had made any official statement on the findings.

The head of the Palestinian investigation team, Tawfiq Tirawi, confirmed on Tuesday that the Russian and Swiss reports had been delivered. The Palestinian team is reported to have handed over its findings on Saturday.